1. Field
The present invention relates generally to a rechargeable battery having an external short-circuit part.
2. Description of the Related Art
Unlike a primary battery, a rechargeable battery can be repeatedly charged and discharged. A small capacity rechargeable battery may be used in a small portable electronic device such as a mobile phone, a laptop computer, or a camcorder, and a large capacity rechargeable battery may be used, for example, as a power supply for driving a motor of a hybrid vehicle, or the like.
Rechargeable batteries include an electrode assembly including a positive electrode and a negative electrode formed on respective surfaces of a separator, a case for receiving the electrode assembly embedded therein, a cap plate closing an opening of the case, and a negative electrode terminal and a positive electrode terminal penetrating through the cap plate and electrically connected to the electrode assembly.
Since the rechargeable battery may be repeatedly charged and discharged, excessive heat may be generated in the case and/or an electrolyte in the case may decompose. The generation of heat or the decomposition of the electrolyte as described above may increase an internal pressure of the rechargeable battery. The increase in the internal pressure may cause ignition or explosion of the rechargeable battery.
Therefore, in order to prevent the ignition or the explosion of the rechargeable battery due to the increase in the internal pressure, the case may be provided with an external short-circuit part. When the internal pressure of the rechargeable battery increases, the external short-circuit part short-circuits the negative electrode and the positive electrode of the electrode assembly at an outer portion of the rechargeable battery. When the external short-circuit part is short-circuited, a current is discharged such that a charging state of the electrode assembly is lowered.
For example, the external short-circuit part may include a connection plate connected to the negative electrode terminal and a membrane installed in a short-circuit hole of the cap plate. The membrane is spaced apart from the connection plate when the rechargeable battery is operating normally. The cap plate and the membrane are connected to the positive electrode terminal. The membrane is configured to be reversed and contact the connection plate when the internal pressure in the rechargeable battery increases.
In conventional short-circuit parts, an outer surface of the cap plate includes a step located along an outer circumference of a terminal hole in the cap plate. The step is configured to fix the membrane on an outer surface of the cap plate. The membrane is welded to the step in the outer surface of the cap plate to close the short-circuit hole. In addition, the connection plate protrudes outwardly from the cap plate and faces the membrane. Accordingly, conventional short-circuit parts may increase the size of the rechargeable battery.
In addition, in conventional short-circuit parts, the space between the membrane and the connection plate is small. Accordingly, when the membrane is reversed due to an increase in internal pressure, the amount of the membrane that contacts the connection plate is increased. Further, the size of conventional membranes is limited to the size of the short-circuit hole in the cap plate. Accordingly, the internal pressure applied to the membrane is limited by the size of the short-circuit hole, Therefore, it may be difficult to uniformly reverse the membrane when the internal pressure in the rechargeable battery increases. Additionally, contact resistance between the membrane and the connection plate may be increased due to the non-uniform reversion of the membrane.
Furthermore, since the weld coupling the membrane to the cap plate is provided on the outer surface of the cap plate, the weld may be exposed to external air, moisture, and foreign materials, which may corrode the weld.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the described technology and therefore it may contain information that does not form part of the prior art.